The present invention relates generally to quantum cascade (QC) lasers and amplifiers, and more particularly to such lasers and amplifiers that operate in the terahertz region of the electromagnetic spectrum.
Quantum cascade lasers operating at terahertz frequencies (1-10 THz, or 30-300 μm in wavelength) are promising sources of radiation in this underutilized portion of the electromagnetic spectrum. For example, terahertz QC lasers are desirable sources for imaging and spectroscopic applications because they are high-powered, and can operate in continuous wave, and can operate over a range of frequencies, e.g., between 1.2 and 4.9 THz. Terahertz QC lasers are not, however, yet portable as they require, e.g., cryogenic cooling for operation.
The use of the metal-metal waveguide structure in terahertz QC lasers has lowered the cooling requirements, e.g., allowing operating temperatures of about 178 K. The tradeoff for this higher temperature operation is lower power levels (10's of milliwatts) and highly divergent emission patterns (>180 degrees). Recently, several research groups have investigated various structures to mitigate these drawbacks. These techniques, however, suffer from a number of shortcomings. For example, they can involve microfabrication of horn antennas within the waveguide, which can be cumbersome. For example, the horn dimensions must be flared to control the beam in order to control divergence, which necessitates three dimensional fabrication techniques.
Accordingly, there is a need for enhanced terahertz QC lasers.